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Comparative metagenomics at Solfatara and Pisciarelli hydrothermal systems in Italy reveal that ecological differences across substrates are not ubiquitous
No full textIntroduction: Continental hydrothermal systems (CHSs) are geochemically complex,
and they support microbial communities that vary across substrates. However, our
understanding of these variations across the complete range of substrates in CHS
is limited because many previous studies have focused predominantly on aqueous
settings.
Methods: Here we used metagenomes in the context of their environmental
geochemistry to investigate the ecology of different substrates (i.e., water, mud and
fumarolic deposits) from Solfatara and Pisciarelli.
Results and Discussion: Results indicate that both locations are lithologically similar
with distinct fluid geochemistry. In particular, all substrates from Solfatara have similar
chemistry whereas Pisciarelli substrates have varying chemistry; with water and mud
from bubbling pools exhibiting high SO4
2− and NH4
+ concentrations. Species alpha
diversity was found to be different between locations but not across substrates,
and pH was shown to be the most important driver of both diversity and microbial
community composition. Based on cluster analysis, microbial community structure
differed significantly between Pisciarelli substrates but not between Solfatara
substrates. Pisciarelli mud pools, were dominated by (hyper)thermophilic archaea,
and on average, bacteria dominated Pisciarelli fumarolic deposits and all investigated
Solfatara environments. Carbon fixation and sulfur oxidation were the most important
metabolic pathways fueled by volcanic outgassing at both locations. Together, results
demonstrate that ecological differences across substrates are not a widespread
phenomenon but specific to the system. Therefore, this study demonstrates the
importance of analyzing different substrates of a CHS to understand the full range of
microbial ecology to avoid biased ecological assessments.Published1066406OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
An updated view of the Italian seismicity from probabilistic location in 3D velocity models: The 1981–2018 Italian catalog of absolute earthquake locations (CLASS)
No full textWe have built a complete catalog of three-dimensional (3D) hypocenter locations of earthquakes recorded in
Italy from 1981 to 2018. Our catalog includes more than 420,000 events relocated by inverting a newly integrated dataset of ~5.0 million P and ~ 3.5 million S wave arrival times recorded by the Italian National Seismic Network and other permanent seismological networks operating in Italy. Available magnitudes are associated with earthquake locations from the most recent datasets and bulletins of Italian seismicity. Earthquakes are located in an updated 3D tomographic model of Italy obtained by including the Moho discontinuity and the seismic velocities of the Ionian subduction zone. We used a probabilistic, non-linear earthquake location code which provides complete information of the hypocenter solution uncertainties. Quality estimators of earthquake locations are analyzed a posteriori with an original criterion for a quantitative classification of the results, allowing users to select seismic events belonging to consistent quality classes and giving a more controlled image of the Italian instrumental seismicity for tectonic and geodynamical studies. The resulting catalog gives a new, coherent view of the spatial and temporal distribution of Italian seismicity. By selecting well constrained located events we construct the new Italian Crustal Seismogenic Layer (CSL) with a good spatial resolution, allowing us to show a comparison between seismogenic thicknesses and Moho geometry distribution. We finally present some examples of seismicity distribution in selected areas of Italy at regional and local scale relating the relocated events of our catalog with available multidisciplinary information from geology, geochemistry, geodynamical models, and historical seismicity.Published229664OST1 Alla ricerca dei Motori GeodinamiciOST2 Deformazione e Hazard sismico e da maremotoOST3 Vicino alla fagliaJCR Journa
Real-time probabilistic assessment of volcanic hazard for tephra dispersal and fallout at Mt. Etna: the 2021 lava fountain episodes
No full textStarting from February 2021, Mt. Etna (Italy) experienced a period of intense explosive activity with 17 lava fountain episodes between 16 February and 1 April 2021. During the eruptive cycle, the Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Etneo (INGV-OE) issued 62 alert notifications known as VONAs (Volcano Observatory Notice for Aviation) to inform the aeronautical authorities about the volcanic activity. We present an automated VONA-based workflow aimed at real-time assessment of the volcanic hazard due to tephra fallout at Mt. Etna. When a VONA reporting tephra emission is issued by INGV-OE, numerical simulations accounting for atmospheric and eruptive uncertainties are automatically initialized to produce probabilistic hazard maps of tephra fallout and atmospheric dispersal. We applied the workflow to three lava fountains that occurred during the 2021 eruptive cycle. To test the modelling results, we compared the simulated ground load with field data, and the extent and position of the simulated volcanic cloud with the observed or estimated volcanic cloud from the Toulouse Volcanic Ash Advisory Center. Overall, we found a good match between simulated and observed quantities (tephra loads and volcanic cloud position), especially when accurate information on eruptive conditions (column height and duration) are supplied by the VONAs. Finally, through a statistical analysis, we found that column height and wind field are fundamental in determining tephra ground accumulation. For this reason, these parameters should be constrained by observational data as accurately as possible when performing numerical simulations, especially in the line of developing operational workflows.Published66V. Pericolosità vulcanica e contributi alla stima del rischioJCR Journa
Cubic Fe-bearing majorite synthesized at 18-25 GPa and 1000 °C: implications for element transport, subducted slab rheology and diamond formation
No full textThe chemistry and mineralogy of slabs subducted into lower mantle control slab rheology and impact the deep volatile cycle. It is known that the metamorphism of little-altered oceanic crust results in eclogite rocks with subequal proportions of garnet and clinopyroxene. With increasing pressure, these minerals react to stabilize pyrope-rich tetragonal majoritic garnet. However, some eclogites contain higher proportions of omphacitic clinopyroxene, caused by Na- and Si-rich metasomatism on the ocean floor or during subduction. The mineralogy of such eclogites is expected to evolve differently. Here, we discuss the results of the crystallization products of omphacitic glass at ~ 18 and ~ 25 GPa and 1000 °C to simulate P-T regimes of cold subduction. The full characterization of the recovered samples indicates evidence of crystallization of Na-, Si-rich cubic instead of tetragonal majorite. This cubic majorite can incorporate large amounts of ferric iron, promoting redox reactions with surrounding volatile-bearing fluids and, ultimately, diamond formation. In addition, the occurrence of cubic majorite in the slab would affect the local density, favoring the continued buoyancy of the slab as previously proposed by seismic observations. Attention must be paid to omphacitic inclusions in sublithospheric diamonds as these might have experienced back-transformation from the HP isochemical cubic phase.Published15855OST1 Alla ricerca dei Motori GeodinamiciJCR Journa
Low-cost drifters: some applications for water monitoring
No full textThis study presents the design and implementation of low-cost drifters, along with different water monitoring applications. The first application presented is related to the tracking of marine litter from the Arno river mouth (central Italy, Tyrrhenian Sea), while the second one concerns the study of the dynamics of a volcanic lake in central Italy (Lago Albano). Both the implementation phase and the field experience benefited from an integrated approach of low-cost equipment, citizen science and numerical modeling.PublishedLa Valletta, MaltaOSA4: Ambiente marino, fascia costiera ed Oceanografia operativ
Assessing the Deep Carbon Release in an Active Volcanic Field Using Hydrochemistry, δ13CDIC and Δ14CDIC
No full textVolcanic activities have great implications on geological carbon cycle, and ascertaining the deep carbon contribution in earth surface that run along the volcanic edifices is important to understand the relationship between solid earth degassing and global climate change. This study reports analytical results of major dissolved ions concentrations, carbon isotopic compositions (δ13CDIC and Δ14CDIC) of dissolved inorganic carbon (DIC) of rivers, cold springs and hot springs from Changbaishan volcanic area, Northeast China. The hydrothermal fluids had a significant impact on solutes budgets, as well as carbon isotopes for the rivers. The changes in concentrations of major ions are mainly controlled by mixing of high-temperature water/rock interaction and low-temperature water/rock interaction, and low-temperature water/rock interaction can be explained by the change of chemical composition between volcanic cone (trachyte) and basaltic shield. We used Δ14CDIC to figure out the contributions of deep carbon and surface carbon. While δ13CDIC was sensitive to CO2 outgassing, and we thus estimated the minimum deep CO2 outgassing yield (1.24×104 t C yr1) based on DIC flux corrected for outgassing by a Rayleigh model. In the Changbaishan volcanic area, deep carbon release flux was higher than CO2 consumption flux by silicate weathering, while the deep CO2 outgassing flux was an underestimate, consistent with the theory that deep CO2 release regulate climate on geological timescales. This study calls for a better understanding of the effects of volcanic activities on earth surface’s carbon cycling, which has great implications on studying global climate change.Publishede2023JG007435OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Site-Dependent Amplification on Topography during the 2016 Amatrice Seismic Sequence, Central Italy
No full textFollowing the Mw 6.0 Amatrice earthquake on 24 August 2016 in central Italy, the Emersito task force of the Istituto Nazionale di Geofisica e Vulcanologia installed a temporary seismic network focusing on the investigation of amplification effects at municipalities located on topographic reliefs. Fourteen stations were installed at three sites: Amandola, Civitella del Tronto, and Montereale. During the operational period, stations recorded about 150 earthquakes with Mw up to 4.7. Recorded signals were analyzed calculating the horizon- tal-to-vertical spectral ratios at single station, using both ambient noise and earthquake waveforms, as well as standard spectral ratios (SSRs) to a reference site. To robustly estimate site amplification at each station of the site amplification effect at each station, the influence of backazimuth and epicentral distance is investigated. With the aim of reproducing the observed amplification pattern, 2D numerical simulations were performed on a section orthogonal to the topography major axis, constrained through in situ geological investiga- tions and geophysical surveys. Although at Montereale site no clear amplification effects were observed, at Amandola site, all stations on the relief consistently detected significant peaks at about 4 Hz and along N120–150 azimuth. At Civitella del Tronto, a proper reference station is missing, implying a misleading of site response evaluation in terms of SSRs. Moreover, even if all stations show amplification in the frequency band 1–3 Hz, the direction of the maximum amplification varies from northeast to northwest. At the three sites, obser- vations were successfully reproduced by 2D numerical models, the latter suggesting that topography alone cannot reproduce data, and the interplay with subsoil velocity structure is needed to produce a clear amplification effect. We conclude that according to the previous articles, rather than the sole topography convex shape, the geophysical structure has often a predominant role in controlling the observed amplification pattern on topography.Published1208–1229OST4 Descrizione in tempo reale del terremoto, del maremoto, loro predicibilità e impattoJCR Journa
The Community Stress-Drop Validation Study—Part II: Uncertainties of the Source Parameters and Stress Drop Analysis
No full textThis paper is the second part of a previous publication (Bindi et al. 2023 DOI: 10.1785/0220230019). All the decompositions of part 1 are organized in a sort of logic tree and mixed-effect regressions are performed to partition the variability into contributions related to duration, attenuation and site-constraint grouping factors. Statistical uncertainties computed in part 1 (i.e., coming from the fit) are compared with epistemic uncertainties associated to the logic tree, and Sammon's maps are used to visualize the impact of the grouping factors on the overall shape of the source spectra.As part of the community stress‐drop validation study, we evaluate the uncertainties of seismic moment M0 and corner frequency fc for earthquakes of the 2019 Ridgecrest sequence. Source spectra were obtained in the companion article by applying the spectral decomposition approach with alternative processing and model assumptions. The objective of the present study is twofold: first, to quantify the impact of different assumptions on the source parameters; and second, to use the distribution of values obtained with different assumptions to estimate an epistemic contribution to the uncertainties. Regarding the first objective, we find that the choice of the attenuation model has a strong impact on fc results: by introducing a depth‐dependent attenuation model, fc estimates of events shallower than 6 km increase of about 10%. Also, the duration of the window used to compute the Fourier spectra show an impact on fc : the average ratio between the estimates for 20 s duration to those for 5 s decreases from 1.1 for Mw4.5. For the second objective, we use a mixed‐effect regression to partition the intraevent variability into duration, propagation, and site contributions. The standard deviation ϕ
of the intraevent residuals for log(fc) is 0.0635, corresponding to a corner frequency ratio 102ϕ=1.33. When the intraevent variability is compared to uncertainties on log(fc), we observe that 2ϕ is generally larger than the 95% confidence interval of log(fc), suggesting that the uncertainty of the source parameters provided by the fitting procedure might underestimate the model‐related (epistemic) uncertainty. Finally, although we observe an increase of log(Δσ) with log(M0) regardless of the model assumptions, the increase of Δσ with depth depends on the assumptions, and no significant trends are detected when depth‐dependent attenuation and velocity values are considered.Published1992–20023T. Fisica dei terremoti e Sorgente SismicaJCR Journa
Comparative Analysis of Methods to Estimate Geodetic Strain Rates from GNSS Data in Italy
No full textOur ability to estimate surface deformation rates in the Central Mediterranean has considerably
enhanced in the last decade thanks to the growth of continuous Global Navigation Satellite
System (GNSS) networks. Focusing on the Apennine/Alpine seismogenic belt, this area offers the
opportunity to test the use of geodetic strain rates for constraining active tectonic processes and
for seismic hazard assessments. Given the importance of geodetic strain rate models in modern
hazard estimation approaches, however, one has to consider that different approaches can provide
significantly different strain rate maps. Despite the increasing availability of GNSS velocity data,
in fact, strain rate models can significantly differ, because of the spatial heterogeneity of GNSS
station locations and inherent strategies in computing strain rates. Using a dense GNSS velocity
dataset, this study examines three methods for estimating horizontal strain rates, described in the
recent literature, and selected to represent approaches of increasing mathematical complexity. The
advantages, drawbacks, and optimal settings of each method are discussed. The main result is an
ensemble of strain rate models that enable the evaluation of epistemic uncertainties in seismicity
rate models constrained by geodetic velocities.PublishedDM531OST2 Deformazione e Hazard sismico e da maremotoJCR Journa
Fault dip vs shear stress gradient
No full textIn the brittle regime, faults tend to be oriented along an angle of about 30° relative to the principal stress direction. This empirical Andersonian observation is usually explained by the orientation of the stress tensor and the slope of the yield envelope defined by the Mohr-Coulomb criterion, often called critical-stress theory, assuming frictional properties of the crustal rocks (μ ≈ 0.6−0.8). However, why the slope has a given value? We suggest that the slope dip is constrained by the occurrence of the largest shear stress gradient along that inclination. High homogeneous shear stress, i.e., without gradients, may generate aseismic creep as for example in flat decollements, both along thrusts and low-angle normal faults, whereas along ramps larger shear stress gradients determine higher energy accumulation and stick-slip behaviour with larger sudden seismic energy release. Further variability of the angle is due to variations of the internal friction and of the Poisson ratio, being related to different lithologies, anisotropies and pre-existing fractures and faults. Misaligned faults are justified to occur due to the local weaknesses in the crustal volume; however, having lower stress gradients along dip than the optimally-oriented ones, they have higher probability of being associated with lower seismogenic potential or even aseismic behavior.Published1002112T. Deformazione crostale attivaN/A or not JC